The solutions back then include reading the element geometry and the references it provides, just like you describe:

You can read the geometry data from the rebar by Rebar.Geometry property. This property requires an Option argument. You need to set the option.ComputeReferences to true. Then read the edge of the rebar, and get the curve from the Edge object. Finally, get the end point reference from the curve.

Response: I already looked at these posts but with no results. When I create the dimension line, a reference is needed. The approach you describe returns a null reference for the edge.

Here are 4 different paths I attempted, with no desired result so far:

Response: Thanks a lot for the response. It is the solution to our problem! We made little adjustments to the code to have plenty of control about what end do we want to dimension, and also we had to project all the curves involved into a shared reference plane due to the fact that if you have more than one rebar (rebar set), the geometry of the rebar is above or beneath the grid line.

Again, thanks a lot for your time and effort.

This thanks is due to Zhong (John) Wu, Boris Shafiro and especially Stefan Dobre.

Newly Created Dimensioning Not Displayed

For another issue or two, on newly created dimensioning not being displayed properly,
Frank @Fair59 Aarssen
once again comes to the rescue:

Basically, you can't use the reference from the curve of the grid (since that is a surface); you have to create a new reference by using the grid element itself: New Reference(Grid). This reference you can then add to the reference array of the Create.NewDimension method. It's the same when dimensioning reference planes.

If you only have the curve information to start with, you need to get the grid element from the curve's reference and then create a new reference from that.

THE Create.NewDimension method expects the reference type of a grid or reference plane to be REFERENCE_TYPE_NONE (for element), not REFERENCE_TYPE_SURFACE.

Simple, Better Grid References for Dimensioning

My colleague Jim Jia adds:

Please also look at the simple and better code to build reference for Grid below; we don't need to retrieve reference from Grid geometry. We verified that this works well: